Long chain polyunsaturated fatty acids such as docosahexaenoic acid (DHA) and arachidonic acid (ARA) are well known for use in infant nutritional formulas, commercially available examples of which include Similac® Advance® Infant Formula and Isomil® Advance® Infant formula, both of which are available from Ross Products Division, Abbott Laboratories, Columbus, Ohio, USA.
It is well known that ARA and DHA are the predominant long-chain polyunsaturated fatty acids in the central nervous system, and it is believed that an adequate dietary supply during infancy is necessary to support optimum neurodevelopment. For example, numerous investigations have been published which indicate that both visual acuity and neurocognitive development are enhanced in preterm infants fed formulas supplemented with ARA and DHA.
It is also generally known that metabolites of the long-chain polyunsaturated fatty acids (i.e. DHA, ARA and eicosapentaenoic acid [EPA]) are important biomediators that can impact growth and body composition through diverse mechanisms. The levels and ratios of these fatty acids in the diet can influence cell membrane properties, cell-to-cell signaling processes, the expression of genes that regulate cell differentiation and growth, and the synthesis of eicosanoids that affect bone metabolism. Animal studies have been conducted and published which suggest that long-chain polyunsatuated fatty acids in the diet can affect both fat mass, fat distribution, and bone metabolism. There is insufficient information, however, regarding the effects of dietary long-chain polyunsaturated fatty acids, especially ARA and DHA, on body composition in neonatal (infant) animals or in humans.
In studies with adult rodents, for example, diets highly enriched in the long-chain n-3 fatty acids, DHA and EPA, from fish oil with no ARA have been associated with lower body fat when compared with diets rich in saturated fat (e.g., lard, MCT oil) or polyunsaturated fatty acids such as linoleic acid (e.g. corn oil). Other studies with adult rats fed diets similarly enriched in DHA and EPA with no ARA had preferential partitioning of ingested energy toward oxidation at the expense of storage, reduced fat mass, decreased fat cell trophic growth, altered expression of genes involved in adipose tissue metabolism, including lipoprotein lipase activity, increased peroxisomal beta-oxidation, reduced adipocyte cell volumes, increased visceral fat hypertrophy, and altered regulation of leptin.
In a published study of preterm infants fed formulas containing DHA and EPA at less than 0.3% of calories for about five months after hospital discharge, it was noted that infants grew slower and had lower fat-free mass, but fat mass was not different than in infants fed the unsupplemented control formulas Others subsequently found that preterm infants fed formulas containing DHA and EPA and ARA or formulas with DHA and ARA did not have slower growth.
It has now been found, however, that infants fed infant formulas containing DHA and ARA, in contrast to the DHA and EPA (no ARA) enriched animal diets referenced above, had an increased lean body mass and a reduced fat body mass as compared to those fed the control formula, all without an effect on the rate of overall growth of the infants.
It is therefore an object of the present invention to provide a method of providing infant formulas supplemented with ARA and DHA wherein the method provides increased lean body mass and reduced fat mass as compared to a control formula, as applied to both term and preterm infants, without having an impact on overall total growth in the infant.